Mechanical performance of steel tubes filled with demolished concrete lumps under axial compression

Abstract

Demolished concrete lumps (DCLs) have been introduced as partial coarse aggregate replacements in concrete casting process. However, limited research works have been performed on sensitive behaviors of slenderness concrete filled steel tube (CFST) filled with fresh concrete (FC) and DCLs under axial compression. Based on the previous research work, orthogonal design method was employed to investigate further mechanical performance. Experimental studied involved 12 columns of CFST with diameter 159 mm and lengths 2000, 2200 and 2400 mm. The ratios of the diameter-to-thickness (D/t) were 79, 53 and 40, while replacement ratios of FC in DCLs were 0%, 20%, 40% and 60%, respectively. The results of experimental tests of the CFST filled with DCLs and FC indicated that ratio of slenderness have a greatest effect on the bearing capacity of slender column under axial compression, followed by the D/t ratio, and the weakest effect was observed for DCLs replacement. DCLs slightly affected the mechanical performances of slender CFST columns, so the ultimate bearing capacity of CFST can ignore the influence of replacement rate of DCLs. To calculate CFST slender column ultimate bearing capacity with DCLs, design codes AIJ, AISC, CE4, CECS 28: 2012, DL/T 5085-1999 were used to predicted ultimate bearing capacity, found that the code CECS 28:2012 was employed for the calculation of slender CFST DCLs filled column bearing capacity under axial compression being comparable accuracy.